its hard to believe, but turning off PP_GFXOFF_MASK that i had with another issue helped? neat!
EDIT: huh. well!
sometimes, when a monitor doesnt turn on (sees no signal) even though it is fully connected, restarting MAY NOT HELP. in such cases i simply unplug and plug the HDMI cable from the dock station (steam deck). however, it spits at me:
kernel: [drm:retrieve_link_cap [amdgpu]] *ERROR* retrieve_link_cap: Read DPRX feature list failed.
kernel: [drm:retrieve_link_cap [amdgpu]] *ERROR* retrieve_link_cap: Read DPRX feature list_1 failed. Addr:0x2214
kernel: amdgpu 0000:04:00.0: [drm] *ERROR* retrieve_link_cap:1936: core_link_read_dpcd (DP_FEC_CAPABILITY) failed
kernel: amdgpu 0000:04:00.0: [drm] *ERROR* No EDID read.
kernel: amdgpu 0000:04:00.0: [drm] *ERROR* dpcd_set_link_settings:1117: core_link_write_dpcd (DP_DOWNSPREAD_CTRL) failed
kernel: amdgpu 0000:04:00.0: [drm] *ERROR* dpcd_set_link_settings:1122: core_link_write_dpcd (DP_LANE_COUNT_SET) failed
kernel: amdgpu 0000:04:00.0: [drm] *ERROR* dpcd_set_link_settings:1150: core_link_write_dpcd (DP_LINK_BW_SET) failed
kernel: amdgpu 0000:04:00.0: [drm] *ERROR* dpcd_set_link_settings:1117: core_link_write_dpcd (DP_DOWNSPREAD_CTRL) failed
kernel: amdgpu 0000:04:00.0: [drm] *ERROR* dpcd_set_link_settings:1122: core_link_write_dpcd (DP_LANE_COUNT_SET) failed
kernel: amdgpu 0000:04:00.0: [drm] *ERROR* dpcd_set_link_settings:1150: core_link_write_dpcd (DP_LINK_BW_SET) failed
kernel: amdgpu 0000:04:00.0: [drm] *ERROR* dpcd_set_link_settings:1117: core_link_write_dpcd (DP_DOWNSPREAD_CTRL) failed
all within 1 second. BUT! it seems to not matter as the monitor is now fully functional 